Heretofore, hollow elastic balls have been made by a variety of processes using different types of apparatus and molding and vulcanizing procedures. Some of these procedures have involved molding semi-spherical hollow halves and thereafter cementing the edges of two abutted halves together. Or, two formed semi-spherical halves are put into spherical shape in a mold by abutting the edges thereof and then the edges can be bonded together by an adhesive between the halves.
In making hollow spherical articles, it is difficult to obtain strong bonds between independently shaped semi-spherical articles, and it also has been difficult to provide a substantially balanced balls without seams inside or outside the hollow ball by known ball making techniques.
It is the general object of the present invention to provide a novel apparatus and method of making hollow spherical balls of vulcanizable materials, and to form such balls from specially vulcanized hollow semi-spherical article shapes.
Another object of the invention is to prevent vulcanization of the edge portion of a semi-spherical elastomeric article when it is in a mold and is heated for vulcanization of the article.
Another object of the invention is to provide an improved apparatus for maintaining an edge portion of a hollow semi-spherical article in a mold cavity cool while vulcanizing the remainder of the semi-spherical article.
Yet other objects of the invention are to provide a novel and improved, relatively uncomplicated and positive method of forming a hollow ball having a sturdy bond between preformed halves of the hollow article.
The foregoing and other objects and advantages of the invention will be made more apparent as the specification proceeds.